Can respec to fulfill a different role = hybrid.
Cannot respec to fulfill a different role = pure.
The roles are tank, healing and damage.
In our design, having two healing trees (priest) or half a tanking tree (druid) or three dps trees (DK) does not put these classes in different categories of hybridness. A hybrid is a hybrid.
It’s the roles that your class lets you do that is important, not how those roles are organized into talent trees. The paladin is one way to organize the trees (a tanking tree, healing tree and melee dps tree) but not the only way. However, there is a reason we don’t do this for every class – it would be boring.
In our design, the pure dps classes (hunter, mage, warlock and rogue) should do slightly higher dps than hybrid damage-dealers all things being equal . All things are rarely equal. Player skill, gear, raid comp, latency, random luck and most importantly the specifics of the encounter will often favor one class, spec or player over another.
The reason we want pures to so slightly higher damage is that pures can only fulfill one role. If your guild or raid has no more need for damage-dealers, there is no way for these classes to raid with you. By contrast, the six other classes always have the option to respec for another role either temporarily or for the long haul.
The Blizzard definition of hybrid in this context has nothing to do with whether you can perform multiple roles within a single fight or even within a single raid. It has more to do with the potential for your class to ever fulfill more than one role.
Likewise, the Blizzard definition of hybrid in this context has nothing to do with the power of certain buffs or class synergy. We want all classes to bring useful tools to the raid.
Just because you’re not interested in doing anything other than damage does not qualify your class as a pure as long as the option to change roles is there. For the pure classes the only option is to reroll. We think the pure classes would start to disappear over time, at least from high-end raiding, if there was no advantage for being a pure. The hybrid advantage is flexibility.
There is not a “5% rule” that says pures should be 5% higher than hybrids in every circumstance. Again, most of the time other factors such as the encounter specifics will have a greater effect. The “5% rule” was either something a player suggested that stuck or something we threw out at some point as an example. It isn’t a hard and fast rule. We aren’t going to provide a hard and fast rule because players would then attempt to invoke that rule every time they thought their damage was too low instead of exploring other ways to improve their character’s performance.
This philosophy largely evolved in Wrath of the Lich King and is the design we plan on carrying forward to Cataclysm. In vanilla WoW, every class typically had one role. In BC, we tried to promote other roles for some classes, but we still didn’t make everyone play by the same rules. Warriors, and I hate to pick on them, were intended to be the best tank while also deliver dps that we would now label as competitive with rogues. By contrast, druids, paladins, priests and shaman were intended to be competitive healers, but have dramatically lower dps than pures and warriors. Likewise, druids, paladins, priests and shaman brought many unique and powerful buffs that were intended to compensate for their low dps. We spread these buffs out to a much greater degree in Lich King, and plan on refining that implementation for Cataclysm.
TLDR:
Hybrid = can respec to fulfill a different role (damage, tanking, or healing).
Hybrid != can fill multiple roles at the same time.
Hybrid != has awesome, amazing buffs or utility.
Hybrid != pure. Beyond that, there are no shades of gray among hybrids.
